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 SID-Maths:

  Frequency:
  ----------

   To calculate the frequency corresponding to the 16-bit value in
   <A HREF="SID0.HTM">$D400</A>+<A HREF="SID1.HTM">$D401</A>, <A HREF="SID7.HTM">$D407</A>+<A HREF="SID8.HTM">$D408</A>, <A HREF="SID14.HTM">$D40E</A>+<A HREF="SID15.HTM">$D40F</A> use the following formula:

    Freq = 16Bit-Value * Phi2 / 16777216 Hz

   where Phi2 is the system-clock, 985248 Hz for PAL-systems,
   1022727 Hz for NTSC-systems.

   A good approximation for both systems is the formula:

    Freq = 16Bit-Value / 17.03

  Pulse-Width:
  ------------

   To calculate the pulse width (in %) corresponding to the 12-bit value in
   <A HREF="SID2.HTM">$D402</A>+<A HREF="SID3.HTM">$D403</A>, <A HREF="SID9.HTM">$D409</A>+<A HREF="SID10.HTM">$D40A</A>, <A HREF="SID16.HTM">$D410</A>+<A HREF="SID17.HTM">$D411</A> use the following formula:

    PulseWidth = (16Bit-Value / 40.96) %

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